Have you ever seen a coin known as a farthing? It has a picture of a wren on it.
In the old days, there used to be four farthings in a penny, 12 pennies in a shilling and 20 shillings in a pound.
As time went on the coins changed, farthings didn't buy very much and stopped being used. Then fifty years ago everything changed. There were only 100 pennies in a pound. These are the coins we use now.
Look out for a special 50p piece celebrating this change. Along with other coin pictures, it has a wren on it!